Yes, it got a # prompt, and entered a "halt" command, instead of
"reboot".

That's how anita has always worked; it has never issued a "reboot"
command. Any subsequent operations such as running the ATF tests
are done in a freshly started qemu VM, not by rebooting the VM used
for installation.

I can get a cut-and-paste of it later (I am at work now), but what it
did was
# halt
system halted

Is this the exact message printed? If so, it explains the hang,
because anita expects to see a response of "halted by root", not
"system halted".

I just ran it again, manually. Here is the bottom of the window:
| e: Utility menu |
|>x: Exit Install System |
+-----------------------------------------------+
# halt
halt
halted by root

Cursor just sits under the 'h' in 'halted' and waits for qemu's expect
to timeout.